Contorted Polycyclic Aromatic Hydrocarbons with Two Embedded Azulene Units.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) with fused five- and seven-membered rings (azulene units) are structurally rare.
• Previous syntheses of such compounds yielded only minute quantities, typically on surfaces.

Purpose of the Study:

• To develop a rational method for synthesizing soluble, contorted PAHs with two embedded azulene units in bulk.
• To investigate the influence of molecular contortion (curvature) on the electronic properties (aromaticity and conjugation) of these novel PAHs.
• To evaluate the photophysical properties, specifically fluorescence, of the synthesized azulene-containing PAHs.

Main Methods:

• A stepwise deprotection strategy involving tert-butyl groups was employed for synthesis.
• A series of three azulene-embedded PAHs with varying degrees of contortion were synthesized.
• Characterization likely involved spectroscopic techniques (NMR, UV-Vis, fluorescence) and potentially X-ray crystallography.

Main Results:

• Successfully synthesized soluble, contorted polycyclic aromatic hydrocarbons containing two embedded azulene units in bulk quantities.
• Demonstrated a synthetic route enabling control over the degree of molecular contortion.
• Observed high fluorescence quantum yields in the near-infrared (NIR) region for the synthesized azulene PAHs.

Conclusions:

• The developed synthetic approach allows for the preparation of novel azulene-embedded PAHs.
• Molecular contortion significantly influences the aromaticity and conjugation of these complex PAH structures.
• The synthesized compounds exhibit promising photophysical properties, particularly strong NIR fluorescence, suggesting potential applications in optoelectronics.